The present invention relates to the tools for machining the surfaces of articles and more particularly it relates to rotary cutting tools, namely needle cutters.
The present invention can be used most successfully for machining metal articles, metallic strips, round bars and pipes, including descaling and derusting, grinding, polishing and other similar operations.
Known in the art at present are rotary cutting tools made in the form of a body of revolution comprising an arbor with sets of cutting elements in the form of pieces of wire which are fixed together at one end and pressed against one another by their side surfaces in close proximity to the fixed ends while their free ends form the cutting surface of the tool and are spaced so densely that the coefficient of filling of the cutting surface by these ends varies from 0.1 to 0.99.
In these known tools the set of the cutting elements is clamped at the sides by washers and is slipped on a bushing which has a hold-down cover and a key at each end.
Such tools can be made for machining articles up to 500 mm wide because it is quite easy to bore out a bushing to the diameter of the shaft throughout the width of the cutting tool and to make a keyway or splines on the bushing.
However, making a tool wider than 500 mm involves certain technological difficultites, namely:
It is difficult to bore out the bushing to the shaft diameter in very wide tools throughout the width of the tool and to make a keyway or splines in such long bushings.
Besides, considerable radial forces arising in the operating tool may cause the middle part of the set of cutting elements to cave in. Therefore, it becomes necessary to provide stops between the inner surface of the set of cutting elements and the bushing; the stops complicate the design of the tool and make disassembly or assembly of the tool troublesome.
In addition, if some part of the set of cutting elements becomes faulty, it cannot be replaced by a new one since this will be prevented by the bushing and stops.
Owing to the difficulties mentioned above the articles wider than 500 mm are now machined with the aid of mechanisms carrying two or three parallel arbors with cutting tools. One arbor carries two or more tools not wider than 500 mm while the gap between said tools is bridged by some more similar tools mounted on another arbor.
Such mechanisms are rather involved and difficult to operate.